Does Growth Hormone Therapy in Conjunction With Resistance Exercise Increase Muscle Force Production and Muscle Mass in Men and Women Aged 60 Years or Older?

• Aging
• Muscle wasting
• Physical activity
• Sarcopenia
• Weight-lifting exercise

Advancing age is associated with a reduction in skeletal muscle protein and muscle force production, a syndrome referred to as sarcopenia. This process occurs during normal aging, but it is accelerated by physical inactivity and degenerative or other disease conditions.¹ Decreased muscle mass and force production are associated with an increased risk of falling² and, therefore, an increased risk for hip fracture.³ Reduced muscle force production with aging can also result in physical disability and frailty¹ and in a loss of independent function,⁴ and it contributes to escalating health care costs.⁵ Our understanding of the mechanisms responsible for sarcopenia is limited. The most obvious intervention is exercise, but the feasibility and effectiveness of exercise in this population are still under investigation. Pharmacological and nutritional interventions for sarcopenia have been proposed,^6–8 but preliminary evidence is not encouraging.^6–15 Efficacious interventions for elderly people need to enhance both muscle protein mass and force production.

The biological consequences of advancing age and the progressive decline in physical activity with age contribute to sarcopenia. Exercise, especially resistance exercise training, has the potential to improve overall fitness and quality of life. The physiological and functional benefits of increased muscle activity, even into the ninth decade of life, have been reported.¹⁶ Thus, human skeletal muscle protein maintains the ability to respond to, and adapt favorably to, exercise-induced increases in contractile activity throughout the life span. The ability to adapt with advancing age, however, may be somewhat limited by other biological processes. For example, circulating concentrations and the pulsatile release patterns of several hormones that regulate metabolism are reduced with advancing age.^{7–9,12,17–21} By virtue of their anabolic actions on body proteins, low serum growth hormone …